1. Field of the Invention
The present invention relates to a liquid discharge head which discharges a liquid and a method of manufacturing the liquid discharge head. The present invention more particularly relates to an ink jet recording head which discharges ink to a recording medium to record an image on the medium and a method of manufacturing the ink jet recording head.
2. Description of the Related Art
Examples of use of a liquid discharge head which discharges a liquid includes an ink jet recording system which discharges ink to a recording medium to record an image on the medium.
The ink jet recording head applied to the ink jet recording system generally includes a plurality of fine ink discharge ports, a plurality of ink flow paths and a plurality of energy generating elements disposed at a part of the ink flow paths. A technology to highly precisely prepare micro structures such as the ink flow paths and discharge ports is required. As such a technology, photolithography is an excellent technology in respect of both of precision and simplicity of steps.
Heretofore, as a method of preparing the ink jet recording head, a method is disclosed in, for example, U.S. Pat. No. 4,450,455, in which an ink flow path pattern is made of a photosensitive resin on a substrate provided with the energy generating elements, a top plate of glass or the like is bonded to the substrate, and then an end surface of the resultant bonded material is mechanically cut to form the discharge ports, thereby preparing the ink jet recording head.
Moreover, in U.S. Pat. No. 4,558,333, a method is disclosed in which the ink flow path and the ink discharge ports are formed of a first photosensitive resin on the substrate provided with the energy generating elements to prepare the ink jet recording head.
On the other hand, since enlargement of the recording head itself and extension of a printing width very effectively achieve increase of a recording speed, investigations of the enlargement and the extension are advanced with respect to the head of each system. On the other hand, an inorganic substance made of silicon or the like is frequently used in the above-mentioned substrate. However, during the preparation of the ink jet recording head, a heating treatment is performed in many cases. Therefore, when a thickness and an area of an ink flow path member increase, warpage and peel are sometimes generated among photosensitive resin layers constituting ink flow path walls and the substrate and the top plate owing to differences of linear expansion coefficients.
In general, the resin material has a linear expansion coefficient larger than that of a material such as silicon for use in the substrate. Therefore, as a method of reducing the linear expansion coefficient of the resin, in general, a method is generally adopted in which the resin is filled with a filler such as amorphous silica. In U.S. Pat. No. 5,510,818, a method of manufacturing the ink jet recording head is disclosed in which an epoxy resin filled with an inorganic filler to reduce the linear expansion coefficient of the resin is used in the ink flow path walls.
However, an average particle diameter of inorganic particles for use as the filler is usually about several tens of μms to several μms. When the photosensitive resin is filled with the filler and exposed, a ray for use in the exposure is absorbed, reflected or scattered, sensitivity of the photosensitive resin is reduced, and resolution also remarkably deteriorates.
On the other hand, when the average particle diameter of the inorganic particles is several hundreds of nanometers to several tens of nanometers, it is considered that the filler is sufficiently transparent to the ray for use in the exposure. However, when the particle diameters of such so-called inorganic fine particles decrease, forces applied between the particles increase, and the particles easily aggregate. Therefore, it is remarkably difficult to singly scatter the inorganic fine particles having particle diameters of the order of nanometers by mechanical kneading. Therefore, even when the average particle diameter is several hundreds of nanometers to several tens of nanometers or less, transparency to the ray for use in the exposure cannot be obtained in some case. Therefore, difficulty remains in fine processing in which the photolithographic technology is used.